Sweet vernal grass
Summary
Sweet vernal grass is a fragrant, perennial, and tufted grass native to cold-temperature zones, mainly pollinating in the spring season. The leaves of this grass are pointed, and flower heads are crowded with spikelets. This species (Anthoxanthum odoratum) thrives across a variety of habitats like wetlands with medium to a high amount of nutrients, forest, roadsides, wastelands, dry grasslands, and sward. Individuals allergic to sweet vernal grass pollen may experience symptoms like allergic rhinitis and asthma after inhalation which is the main route of exposure. Ant o 1 is reported as the major allergenic component of sweet vernal grass. Cross-reactivity is evident within the Poodieae subfamily, including grasses like brome, fescue, ryegrass, June, timothy, orchard, sweet vernal, velvet, and canary. Clinical cross-reactivity between Anthoxanthum odoratum and Limonium sinuatum (lavender) has also been reported. Due to the conserved structure and ubiquitous distribution, polcalcin and profilin are also found to be cross-reactive. The cross-reactivity of Anthoxanthum odoratum (sweet vernal grass) is also observed with the wheat pollen (Triticum aestivum).
Epidemiology
Worldwide distribution
Around 20% of the general population and almost 40% of the atopic individuals are impacted by allergic sensitization due to grass pollens. Sweet vernal grass pollens mainly cause seasonal respiratory symptoms, such as asthma, rhinitis and conjunctivitis.
Anthoxanthum spp. are considered one of the most widespread genera responsible for the manifestation of allergy in the Northern Hemisphere and adds to the broad spectra of allergy-causing pollens from grass.
According to a study conducted on 184 Costa Rican patients with allergic rhinitis (AR) (tested for sensitivity to Poaceae species), A. odoratum demonstrated 83.2% (highest percentage) of positive skin prick test reports.
Route Of Exposure
Main
Inhalation is one of the exposure routes for the pollens belonging to the Poaceae family.
Clinical Relevance
Studies have reported that inhalation of airborne pollen adversely impacts the respiratory system of genetically predisposed individuals and individuals who later developed hypersensitivity. This further results in hypersensitivity disorders like AR and asthma.
Allergic rhinitis
Pollen from grasses belonging to the Poaceae family is reported to be a significant contributor to outdoor aeroallergen. Further, it is claimed that a greater number of individuals are sensitized to grass pollens compared to any other pollen type.
An Istanbul-based study on 2822 AR patients (aged: 2 to 18 years) demonstrated that 11.1% (314/2822) exhibited positive skin allergy tests towards sweet vernal grass allergens. Moreover, sweet vernal grass was also reported as the second susceptible category of allergen among children with AR.
Asthma
The pollutants present in the air adversely impact the lung function in asthmatic patients, specifically children. The ingression of inhaled allergens into the cells of the immune system is further accelerated by the impaired mucous membrane of the respiratory system, caused by air pollutants.
A Turkey-based study was conducted on 125 patients (with rhinitis and/or asthma) to estimate the incidence of sensitivity towards pollens. 100 patients exhibited allergy to a minimum of one pollen. 45% (45/100) of patients reported sensitivity towards A. odoratum. The Poaceae family was also reported as a frequent aeroallergen source among pollen sensitized individuals with asthma and/or rhinitis within the study region.
Prevention And Therapy
Prevention strategies
Avoidance
One of the main measures to be taken is to cut down the pollen amount in the respiratory system. During the pollen season, allergic patients are suggested to stay indoors or wear a mask outdoors to keep away from pollen allergens. In worsening conditions, patients might be advised to move to a pollen-free area.
Cross-Reactivity
Cross-reactivity has been observed between grasses of the Pooideae subfamily due to the remarkable homology of major allergen groups 1, 2/3, and 5. This group is prevalent in various members of the grass family like timothy, orchard, velvet, sweet vernal, ryegrass, June, brome, fescue, and canary grasses. The cross-reactivity of A. odoratum (sweet vernal grass) is also observed with the wheat pollen (Triticum aestivum).
According to a study, a 42-year-old woman (owner of a greenhouse and floral shop) with no history of atopic diseases have reported dyspnea and wheezing while handling fresh Limonium sinuatum (lavender) flowers. On further investigation, the patient exhibited a positive skin test reaction towards A. odoratum pollen. Cross-reactive epitopes between A. odoratum and L. sinuatum might be responsible for the manifestation of respiratory allergies in this patient.
As per a study, the conserved structure and ubiquitous distribution of polcalcin and profilin are claimed to be responsible for exhibiting cross-reactivity in between these proteins.
References
- Tava A. Coumarin-Containing Grass: Volatiles from Sweet Vernalgrass (Anthoxanthum odoratum L.). J Essent Oil Res, 13, 367-370. 2001.
- Lambrechtsen. SOME ASPECTS OF THE BIOLOGY OF ANTHOXANTHUM ODORATUM L. A Thesis presented for the degree of Doctor of Philosophy in Botany in the University of Canterbury, Christchurch, New Zealand. 1968.
- Lawniczak AE. Response of Anthoxanthum odoratum and A. aristatumto different habitat types and nutrient concentrations in soil. Fresenius Environmental Bulletin 20(9A):2465-2474. 2011.
- Alm T. Scented grasses in Norway--identity and uses. J Ethnobiol Ethnomed. 2015;11:83.
- CABI. Anthoxanthum odoratum (sweet vernal grass). 2020 [23-12-2020]. Available from: https://www.cabi.org/isc/datasheet/93023.
- Diehn S, Zimmermann B, Tafintseva V, Bagcioglu M, Kohler A, Ohlson M, et al. Discrimination of grass pollen of different species by FTIR spectroscopy of individual pollen grains. Anal Bioanal Chem. 2020;412(24):6459-74.
- Halbritter. Anthoxanthum odoratum 2016. Available from: https://www.paldat.org/pub/Anthoxanthum_odoratum/301909.
- WHO/IUIS. WHO/IUIS Allerger Nomenclature Anthoxanthum Odoratum 2020 [23/09/2020]. Available from: http://www.allergen.org/viewallergen.php?aid=57.
- Andersson K. Characteristics and immunobiology of grass pollen allergens. Int Arch Allergy Immunol. 2003;130(2):87-107.
- Ullmann N. Unusual cause of dyspnoea. Arch Dis Child Educ Pract Ed. 2018;103(6):300-1.
- Harmanci E. The type of sensitization to pollens in allergic patients in Eskisehir (Anatolia), Turkey. Allergol Immunopathol (Madr). 2000;28(2):63-6.
- Garcia-Mozo H. Poaceae pollen as the leading aeroallergen worldwide: A review. Allergy. 2017;72(12):1849-58.
- Riggioni O, Montiel M, Fonseca J, Jaramillo O, Carvajal E, Rosencwaig P, et al. [Type I hypersensitivity to gramineae pollen (by species) in allergic rhinitis patients]. Rev Biol Trop. 1994;42 Suppl 1:71-6, 20.
- Pimentel M, Sahuquillo E, Torrecilla Z, Popp M, Catalan P, Brochmann C. Hybridization and long-distance colonization at different time scales: towards resolution of long-term controversies in the sweet vernal grasses (Anthoxanthum). Ann Bot. 2013;112(6):1015-30.
- Singh AB. An aerobiological perspective in allergy and asthma. Asia Pac Allergy. 2012;2(3):210-22.
- Brennan GL, Potter C, de Vere N, Griffith GW, Skjoth CA, Osborne NJ, et al. Temperate airborne grass pollen defined by spatio-temporal shifts in community composition. Nat Ecol Evol. 2019;3(5):750-4.
- Özçeker. D. Allergy Skin Tests in Inner-City Children with Allergic Rhinitis Living in İstanbul. . Eur Arch Med Res 2018; 34 (4): 258-61. 2018.
- Xie Z-J, Guan K, Yin J. Advances in the clinical and mechanism research of pollen induced seasonal allergic Asthma. American journal of clinical and experimental immunology. 2019;8(1):1.
- Niederberger V, Laffer S, Froschl R, Kraft D, Rumpold H, Kapiotis S, et al. IgE antibodies to recombinant pollen allergens (Phl p 1, Phl p 2, Phl p 5, and Bet v 2) account for a high percentage of grass pollen-specific IgE. J Allergy Clin Immunol. 1998;101(2 Pt 1):258-64.
- Sastre J. POLCALCINS. C06. PART CCROSS-REACTIVE MOLECULES & THEIR CLINICAL RELEVANCE. P M Matricardi, J Kleine-Tebbe" EACCI MOLECULAR ALLERGOLOGY USER’S GUIDE. 2016:337-44.
- Grote M, Swoboda I, Valenta R, Reichelt R. Group 13 allergens as environmental and immunological markers for grass pollen allergy: studies by immunogold field emission scanning and transmission electron microscopy. Int Arch Allergy Immunol. 2005;136(4):303-10.
- Weber. Guidelines for using pollen cross-reactivity in formulating allergen immunotherapy. 2008;CLINICAL PEARLS| VOLUME 122, ISSUE 1, P219-221, JULY 01, 2008.
- Gangl K. Marker Allergens and Panallergens in Tree and Grass Pollen Allergy. Molecular Allergy Diagnostics (pp203-226). 2017.
- Vidal C. Occupational asthma to fresh sea lavender and cross-reactivity to sweet vernal grass pollen. Ann Allergy Asthma Immunol. 2007;99(6):576-7.
- Scala E RA, VerenamNiederberger, V. TREE POLLEN ALLERGY. B01. PART B USING MOLECULAR ALLERGOLOGY IN THE CLINICAL PRACTICE. P M Matricardi, J Kleine-Tebbe EACCI MOLECULAR ALLERGOLOGY USER’S GUIDE. 2016:71-83.